Canadian Forest Service Publications
Improving the stability of oriented strand board manufactured from mountain pine beetle wood. 2009. Semple, K.; Cullis, I.; Evans, P. Natural Resources Canada, Canadian Forest Service, Pacific Forestry Centre, Victoria, BC. Mountain Pine Beetle Working Paper 2009-18. 61 p.
Available from: Pacific Forestry Centre
Catalog ID: 31194
Oriented strand board (OSB) accounts for a large share of the market for sheathing and sub-floor underlay, but because of its lower dimensional stability when exposed to moisture, it has not completely replaced plywood. The manufacture of OSB represents one of the major ways in which value can be recovered from mountain pine beetle-killed wood. Large amounts of beetle-killed wood are being processed into OSB in western Canada. The main challenges associated with using this wood for oriented strand board are log dryness, greater brittleness, and the wood's propensity to break up into smaller fragments during the production of board strands, which reduces the composite's moisture resistance and dimensional stability. Log rehydration and modification of pressing schedules for OSB have enabled beetle-killed wood to be used in commodity-board production, but need remains to develop practical solutions to the problem of high water absorption and thickness swelling of boards. This project investigated a range of different coating and water-repellent technologies to reduce moisture absorption and thickness swelling of OSB made from mountain pine beetle wood. We found linseed oil mixed with wax or expandable plastic microspheres provides effective short-term resistance to water absorption and thickness swell, but longer-term protection is compromised by the gradual deterioration of hardened linseed oil by water. Industrial coatings-application methods, including spraying and high-speed roller coating, were tested to apply micro-structured water repellents, oils and ultraviolet-cured coatings to OSB surfaces.